The Proteomics Core (Core D) will be responsible for providing the investigators of this Program Project with the proteomics data necessary to achieve their experimental aims. Unique methods (differential mass spectrometry) and extensive experience with proteomics on complex biologic materials will be utilized to discover circulating biomarkers of old age and proteins released from cells that promote cell senescence or tissue regeneration. By coordinating proteomic analyses within this Core, it will be possible to standardize methods and quality control, which will dramatically improve the sensitivity ofthe proteomics approaches. Comparisons between data sets produced for individual projects will significantly increase the value of each data set. For example, are factors secreted by young stem cells, which promote tissue regeneration (Project 3), also detected in the serum of Ercc1-/delta mice chronically treated with an inhibitor of NF-kB (Project 2) or a potent mitochondrial-targeted radical scavenger (Project 1), both of which promote health span and longevity? Comparisons between data sets will also greatly facilitate establishing priorities for which proteins/peptides to pursue. For example, a pro-longevity/anti-senescence factor is predicted to be secreted from young stem cells but not old stem cells or senesent cells/tissues. The same factor might also be induced by pro-longevity interventions (anti-oxidants, NF-kB inhibitors, stem cell therapy) but should not be induced by damaging agents (oxidants, genotoxins, old stem cells) allowing biology to dictate relative importance. In contrast, a single proteomics analysis for one project is comparatively extremely difficult to interpret because it yields a list of proteins/peptides and their relative abundance, which is not necessarily a determinant of biological importance. Hence this proteomics core as part of this Program Project is optimized to overcome several barriers impeding progress in the field and to have the greatest likelihood of identifying secreted and/or circulating factors that affect health span and lifespan. This will yield novel information about mechanisms of aging at the molecular level